1. Field of the Invention
The present invention relates to a purifier that separates overtail rich with bran (skin portion) from semolina (fragments of varying particle size) or middlings (relatively coarse albumen particles fragmented by a brake roll) produced in a flour-milling process by using a vibrating operation of sieves and an action of an air flow passing from a lower portion to an upper portion of the sieves to obtain pure semolina.
2. Description of Related Art
An example of a conventional purifier is disclosed in Japanese Examined Patent Publication No. 1-22827 (refer to FIG. 18). This purifier has an air distribution chamber 122 on a sieve layer 103. The air distribution chamber 122 is provided with a plurality of air guide chambers 124 formed of inclined surfaces 111 of the air distribution chamber 122 inclined in a direction of gathering an air flow from the sieve layer 103 and barrier walls 123. These air guide chambers 124 reach near the top sieve layer 103. On the air distribution chamber 122, a suction passage 127 formed of a horizontal cyclone is placed. Furthermore, a transition portion from the air distribution chamber 122 to the suction passage 127 is constructed toward a tangent direction of the suction passage 127 so that an air flow gathered by the inclined surfaces of the air distribution chamber 122 directly forms a swirl with respect to the suction passage 127. At this transition portion, an aperture 128 is disposed.
With this, a cyclone flow occurs in the suction passage 127 by the tangent-direction transition portion. For example, in the suction passage 127, a strong swirl is formed on one side irrespectively of the degree of opening of the aperture 128, thereby achieving an effect of reliably keeping the machine clean without deposition of dust and other particles or clogging of the aperture opening.
However, in the purifier described in Japanese Examined Patent Publication No. 1-22827, the suction force near the center of the sieve layer 103 in a width direction (an X direction) is strong, while the suction force near both ends in the width direction is weak, thereby making it difficult to uniformly suck powder in the width direction.
Another example of the conventional purifier is disclosed in European Patent Application Publication No. EP0334180 A2. In the purifier disclosed in European Patent Application Publication No. EP0334180 A2, at least one box-like body is rigidly coupled onto a base via elastic elements. The box-like body has two rows of three stacked sifters provided at its middle position, at least one suction hood provided at an upper position, and at least one product collector provided at a lower position.
On the other hand, Japanese Unexamined Patent Application Publication No. 8-39002 discloses a purifier that has pressing bodies for sieves. That is, in paragraph [0013], “A screening device 2 of a purifier 1 has sieve nets 6 multi-layered in three layers . . . . The rear ends 6, 6, 6 of the sieve nets formed in three layers are fixed by sieve pressing bodies 12A, 12B, 12C, respectively, with the pressing body 12A being provided with an opening 13A, the pressing body 12B being provided with an opening 13B, and the pressing body 12C being provided with an opening 13C. The openings 13A, 13B, 13C communicate with a takeout gutter 14 via delivery gutters 8A, 8B, 8C, respectively”. The openings 13A, 13B, 13C provided by piercing the pressing bodies 12 of the respective stages have a separating function of guiding overtail to the discharge gutters 8 for each sieve net 6, and the pressing body 12 at each stage has a sealing function for preventing a leak of powder.
However, in the pressing bodies for the sieve nets described in Japanese Unexamined Patent Application Publication No. 8-39002, after the sieve nets 6 are inserted in a housing, the pressing bodies merely close the opening of that housing for clamping, and are not configured to be able to adjust the pressing force. Therefore, for example, when a plurality of sieve nets with different meshes (wire gauges) are disposed in one layer (in the purifier disclosed in Japanese Unexamined Patent Application Publication No. 8-39002, four sieve nets are disposed in a stock-moving direction), if the pressing force cannot be adjusted, the pressed contact action between the sieve nets is insufficient, resulting in the occurrence of “rattle”, which puts the purifier under violent vibrations at screening. Thus, the sealing function for preventing a leak of powder disadvantageously becomes insufficient.
Still another example of the conventional purifier is disclosed in Japanese Examined Patent Publication Nos. 1-13916 and 1-13917. The purifier disclosed in these patent gazettes and also in Japanese Examined Patent Publication No. 1-22827 has a vibration mechanism, which is now described below with reference to FIGS. 18 to 20. The purifier has a duplex structure in which three stacked sieve layers 103 are unitized as one screening box 108 and two screening boxes 108 are arranged in two rows. Each screening box 108 is supported by an end support 112 onto a support base leg 110 of a support base 109 via a hollow rubber spring 113, and an unbalanced vibration generating device 114 is coupled stiff to the end supports 112. Each screening box 108 can generate linear vibration in a direction indicated by an arrow A in FIG. 19, while the support base leg 110, a column 121, the air distribution chamber 122, a support base head 111, and the suction passage 127, in FIG. 20, all of which are non-vibration components, are not vibrated.
In the purifier disclosed in Japanese Examined Patent Publication Nos. 1-13916, 1-13917, and 1-22827, two vibration generating devices vibrating in reverse directions are used to produce a vibrating motion in a straight inclined direction indicated by the arrow A in FIG. 19. However, supported by the hollow rubber springs 113 inserted in four end supports 112, the screening boxes 108 can freely move in an axial direction (a direction indicated by an arrow Y) and a lateral direction (a direction indicated by an arrow X) of the end supports 112 (refer to FIG. 20).
That is, during a period in which a small number of vibration at the time of starting and stopping the operation, the vibrating direction is unstable, and rolling of the screening boxes 108 occurs not only in the original linear vibrating direction (a direction indicated by an arrow A in FIG. 19) but also in a direction indicated by an arrow X in FIG. 20 (a depth direction in FIG. 19) to cause load stress to repeatedly act on the plurality of non-vibration components, possibly leading to fatigue breakdown.